Thanks for your reply, I will do as you suggest.
The cause appears to be Epstein-Barr virus I had 4 years back. Apart from this, and from the fact that doctors managed to reduce the number of extrasystoles although not eliminate them, I don't know much. The cardiologist did say my heart is "healthy and strong" and that there shouldn't be any problem, but given that she is not an AME, I was worried she might be giving too optimistic assessment. Thanks again.